Sandpipers achieve world record for sleeplessness

You may think you can cope without sleep, but you have nothing on male pectoral sandpipers. Some of these birds can go more than a fortnight with hardly any sleep – the most extreme case of uninduced sleep deprivation known in any animal.

What's more, the males that sleep the least father the most offspring, suggesting they benefit from their lack of slumber.

Pectoral sandpipers (Calidris melanotos) breed on the Arctic tundra of Asia and North America. Males don't help with childcare – instead they try to mate with as many females as possible.

Bart Kempenaers of the Max Planck Institute for Ornithology in Seewiesen, Germany and colleagues fitted radio tags to 149 birds – accounting for most of a population living near Barrow in Alaska. This showed that males were highly active during periods when females were fertile. One male was active 95 per cent of the time for 19 days.

The team then fitted 29 of the males with devices that recorded their brain activity, something never done before with a wild bird. This allowed them to look at the active males' sleep patterns.

They found that the males that slept the least slept more deeply, but calculations show that this wouldn't make up for the sleep they missed, says team member Niels Rattenborg.

No sleep 'til fatherhood

The tracker data showed that the most wakeful males interacted with more females than those that slept. Paternity tests showed that they sired more young.

The study is a rare insight into natural, uninduced sleep deprivation. Most animals feel an intense drive to sleep if they have gone without for a long time. Kempenaers's study shows sandpipers resist that drive for longer than any animal ever tested.

That might have something to do with the location of their breeding grounds. They get 24-hour daylight throughout the breeding season, so wakeful males can court every passing female. This may have created the pressure for them to evolve the ability to go without sleep.

Evolution of snooze

Most sleep researchers assume that sleep restores the body in some way, perhaps giving the brain a chance to recharge its batteries or allowing time for memories to be properly processed. But it's not clear whether sleep is truly essential.

However, even animals that appear to do without sleep find ways to get some, suggesting that it's impossible to do without it entirely. Rattenborg points out that the most sleep-deprived sandpipers compensate by sleeping more deeply. "Sleep is still doing something important for them," he says.

The wakeful sandpipers might also be sneaking in micro-sleeps, says Chiara Cirelli of the University of Wisconsin-Madison. Last year she found that small clusters of neurons in rat brains can fall asleep independently, even though the rest of the brain is awake (Nature, DOI: 10.1038/nature10009). The sandpipers might do the same thing.

If you would like to reuse any content from New Scientist, either in print or online, please contact the syndication department first for permission. New Scientist does not own rights to photos, but there are a variety of licensing options available for use of articles and graphics we own the copyright to.